Cold tube bending with outer bend wall thickness control



H. J. STEEL July 1, 1969 COLD TUBE BENDING WITH OUTER BEND WALL THICKNESS CONTROL Filed Oct. 12, 1967 J H m m July 1, 1969 STEEL 3,452,570-

COLD TUBE BENDING WITH OUTER BEND WALL THICKNESS CONTROL Filed Odt. 12, 1967 Sheet L of 3 INVENTOR HOMER J STEEL H. J. STEEL July 1, 1969 COLD TUBE BENDING WITH OUTER BEND WALL THICKNESS CONTROL Sheet of :5

Filed Oct. 12, 1967 rvh @mYmxmYmw$96 United States Patent 3,452,570 COLD TUBE BENDING WITH OUTER BEND WALL THICKNESS CONTROL Homer J. Steel, 925 Madera Circle, Elm Grove, Wis. 26003 Filed Oct. 12, 1967, Ser. No. 674,819 Int. Cl. B2111 9/05, 7/04 US. Cl. 72-156 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to cold tube bending with outer bend wall thickness control, and comprises an improvement on some of the concepts disclosed in the'present inventors copending United States application Ser. No. 634,519, filed Apr. 28, 1967 and entitled Cold Bending of Tubes. That application, in turn, is an improvement over the present inventors United States Patents 3,243,- 873 and 3,243,982, issued Apr. 5, 1966.

In the above-mentioned copending application Ser. No. 634,519, a device is disclosed wherein means are provided to confine the outer bend wall of the tube in such a manner during forming that the circumferential speed of the outer radius fibers of the bend is the same as the lineal speed of the pressure plunger, to thereby maintain a constant length of the outer bend fibers and thereby maintain a constant thickness of the outer :bend wall throughout. In that application, an intricate hydraulic mechanism is provided to accomplish the stated purpose, and which is manually adjustable.

It has been found that difficulties may arise in making the necessary adjustments in a variable control to maintain the desired relationships. The present invention solves these difficulties in a surprisingly effective manner, and is believed to be particularly useful in cold bending of relatively long tubes.

Broadly, in accordance with the invention, the variable hydraulic control is eliminated and a direct mechanical connection is provided between the lead end and trailing end of the bending mechanism. More particularly, the portion of the tube to be bent is secured between a leading clamp and a trailing clamp. The leading clamp is driven to move the tube about a rotary former, while the trailing clamp is mounted on a carriage for linear movement on suitable ways. To maintain a constant length of the outer tube fibers during forming, the two clamps are mechanically coupled together, as by a chain means.

The accompanying drawings illustrate the best mode presently contemplated by the inventor for carrying out the invention.

In the drawings:

FIGURE 1 is a schematic top plan view of a device constructed in accordance with the invention;

FIG. 2 is a view similar to FIGURE 1, during or after bending;

FIG. 3 is a section taken on line 33 of FIGURE 1; FIG. 4 is a section taken on line 44 of FIG. 3;

FIG. 5 is a view similar to FIGURE 1, and showing another embodiment; and

FIG. 6 is a view similar to FIG. 5, during or after bending, and with parts broken away.

As shown schematically in the drawings, the apparatus embodying the concept of the invention may comprise an elongated base 1 having suitable framework thereon. Base 1 supports a pair of ways 2 at one end, which in turn, have a carriage 3 mounted for sliding movement thereon. Carriage 3 fixedly supports a trailing clamp 4 of any suitable type for securing thereon a trailing portion of a tubular workpiece blank to be bent. In this instance, the workpiece is shown as a relatively long pipe 5.

The other end of base 1 supports a forming apparatus, which may be generally similar to those shown in my above-identified patents and application. As shown in the drawings, the forming apparatus comprises a forming roller 6 mounted for rotation on a vertical axis, and having a roller shaft 7 therebeneath which is mounted in suitable rotary bearings 8 on base 1. Roller 6 is provided with a forming groove 9 on its periphery which is adapted to receive pipe 5 during bending.

For purposes of supporting the leading portion of pipe 5, a support, which includes a leading clamp 10 of any suitable type, is connected or mounted in any suitable manner to roller 6 or its shaft 7 for pivoting about the roller axis. Clamp 10 includes portions '11 which overlap roller 6 and extend outwardly beyond the roller periphery and contain anchor pins 12 located at a distance preferably equal to the radius of groove 9 and pipe 5 beyond the roller periphery.

Roller 6 is adapted to be drivingly rotated about its axis. For this purpose, the lower end of roller shaft 7 is provided with a pinion 13 thereon. Pinion 13 meshes with a pair of racks 14 which, in turn, are each drivingly moved by the outer end of piston rods 15 disposed in hydraulic cylinders 16. This apparatus is suitably mounted on base 1, with cylinders 16 controlla bly receiving hydraulic fluid through lines 17 from any suitable source, not shown.

The portion of pipe 5 which is to be bent is disposed between clamps 4 and 10, and means are provided to support the pipe walls as the pipe approaches the forming mechanism. For this purpose, a grooved supporting shoe 18 and a grooved pressure die '19 are mounted on each side of the entrance to the roller. Die 19 is fixed in the embodiment of FIGS. 1-4.

As best shown in FIGURES 1 and 2, pipe 5 is bent by clamping it in clamp 4 (which i substantially behind the entrance to roller 6) and by clamping it in clamp 10 (which is slightly ahead of the entrance to roller 6). Actuation of piston rods 15 will cause forming roller 6 to turn on its axis, thereby pulling pipe 5 circumferentially around the bend. Assuming that carriage 3 is freely movable on ways 2, the trailing clamp 4 and trailing end of pipe 5 will follows arong linearly.

It has been found that as pipe 5 travels around the bend, the fibers of the outer bend wall 20 will tend to stretch during forming. The resultant bend structure will thus have an outer bend wall which is thinner than cor responding straight pipe portions ahead of and behind the bend. Such variance in outer bend wall thickness is undesirable due to strength requirements and other factors.

The invention contemplates prevention of this problem by keeping the distance between clamps 4 and 10 along the bending path constant, thus maintaining a constant length of the outer bend fibers during forming.

In accordance wih the invention, a direct mechanical linkage is provided between clamps 4 and 10. Before bending of the tube, this linkage joins the clamps in a plane 21 parallel to the roller axis and tangential to the outer wall of the pipe 5. (See FIG. 3.) In the embodiment shown in the drawings, this mechanical linkage embodiment shown in the drawings, this mechanical linkage comprises a pair of parallel flexible chains 22 of fixed length extending between clamps 4 and 10 and connected to the clamps at their ends. In the case of leading clamp 10, the connection is to anchor pins 12. Chains 22 are properly guided by annular toothless sprockets 23 on roller 6.

It is important that the radial distance from the roller axis to the chain center line be approximately equal to the radial distance from said axis to the outer fibers of pipe 5 at all points. This relationship must be maintained throughout the bending operation.

When roller 6 is drivingly turned and clamp 10 moves about the roller axis, chains 22 will not stretch but will remain of constant length, and since their center line path corresponds with the path of the outer bend fibers, these fibers remain of constant length. The distance between the clamps along the bending path remains constant. Thus, the outer bend wall of pipe 5 cannot stretch, and the effect is that the outer pipe wall can be under compression, but in any case is maintained within the elastic limit of the metal.

In some instances, it may be desirable to lighten the load on the chains (or chain, as the case may be). For this purpose, carriage 3 may be connected through a piston rod 24 to a suitably actuatable air cylinder 25 which is supplied with air through lines 26 to any wellknown suitable air source, not shown. Cylinder 25 may be controlled by any well-known valve, not shown to provide advance and retract car-riage motions. It must be, kept in mind, however, that the advance carriage motion must not be sufficient to overcome the tension of chains 22 during forming. After forming, the pneumatic device can be utilized to retract carriage 3 to starting position.

In some instances, such as to reduce scoring of pipes 5 in the pressure die, it may be desirable to make the pressure die movable. In the embodiment shown in FIGS. 5 and 6, carriage 3 is provided with a forward extension and pressure die 27 is slideably mounted thereon. Thus, during forming, pressure die 27 will move longitudinally with the trailing clamp 4 and pipe 5. Also, if desired, the pressure die may include a suitable toggle 28.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. In an apparatus for cold bending of tubes:

(a) a forming roller having a groove therein for receiving a tube during bending,

(b) drive means for rotating said roller about its axis,

(c) a leading clamp connected to said roller for securing the leading pipe portion, said clamp rotating with said roller about said axis,

(d) a linearly movable trailing clamp for securing the trailing pipe portion,

(e) and a mechanical linkage connecting said clamps and disposed to maintain the distance between said clamps, along the bending path constant to thereby maintain a constant length of the outer bend fibers of said tube.

2. The apparatus of claim 1 in which said mechanical linkage comprises at least one chain having its ends attached to said clamps and extending therebetween.

3. The apparatus of claim 1 in which said mechanical linkage comprises at least one link of fixed length having its ends attached to said clamps so that the radial distance from the axis of said roller to the center line of said link it approximately equal to the radial distance from said axis to the outer fibers of the tube.

4. In an apparatus for cold bending of tubes:

(a) a base,

(b) a forming roller on said base with said roller having a groove therein for receiving a tube during bending,

(c) drive means on said base for rotating said roller about its axis,

In nwum nlqmn rnnnertferl to said roller for securing the leading tube portion ahead of said roller, said clamp rotating with said roller about said axis,

(e) a carriage mounted on said base for generally free linear advance movement toward said roller,

(f) a trailing clamp secured to said carriage and adapted to secure the trailing tube portion behind said roller,

(g) a rotation of said roller causing the leading portion of the tube to be formed into a circumferential bend about said roller, with the trailing tube portion moving linearly with said trailing clamp and carriage,

(h) and a mechanical linkage connecting said clamps and disposed to maintain the distance between said clamps along the bending path constant to thereby maintain a constant length of the outer bend fibers of said tube.

5. The apparatus of claim 4 in which said mechanical linkage comprises at least one chain of fixed length having its ends attached to said clamps and extending therebetween.

6. The apparatus of claim 4 in which said mechanical linkage comprises at least one link of fixed length having its ends attached to said clamps and extending therebetween in a manner, so that the radial distance from the axis of said roller to the center line of said link is approximately equal to the radial distance from said axis to the outer fibers of the tube.

7. The apparatus of claim 5 which includes: toothless sprocket means on said roller for guiding said chain.

8. The apparatus of claim 4 which includes: means separate from said mechanical linkage to provide a force on said carriage in the advance direction during forming.

9. The apparatus of claim 8 in which said means separate from said mechanical linkage includes: means to retract said carriage to normal position after forming.

10. In the apparatus of claim 4: a pressure die mounted on said carriage for supporting a wall portion of said tube adjacent the entrance to the roller groove, said pressure die moving linearly with said trailing clamp and carriage during bending.

11. In an apparatus for cold bending of tubes:

(a) a forming roller having a groove therein for receiving a tube during bending,

(b) drive means for rotating said roller about its axis,

(0) a leading clamp connected to said roller for securing the leading pipe portion, said clamp rotating with said roller about said axis,

((1) a linearly movable carriage mounted for generally free linear advancement movement toward said roller,

(e) a trailing clamp secured to said carriage and adapted to secure the trailing tube portion behind said roller,

(f) rotation of said roller causing the leading portion of the tube to be formed into a circumferential bend about said roller, with the trailing tube portion moving linearly with said trailing clamp and carriage,

(g) a mechanical linkage of fixed length connecting said clamps and movable therewith,

(h) and a pressure die disposed adjacent the entrance to the roller groove, said pressure die being mounted on said carriage and thereby connected with said trailing clamp for linear advance movement therewith during tube bending.

References Cited UNITED STATES PATENTS 2,357,006 8/1944 Johnson 72154 3,205,690 9/1965 Roessler 72159 RONALD D. GREFE, Primary Examiner.

US. Cl. X.R. 

